There is known a head mounted display apparatus (a head mounted display (HMD)) which is a display apparatus mounted on the head. For example, the head mounted display apparatus generates image light for an image using a liquid crystal display and a light source, and leads the generated image light to the eyes of a user using a projection optical system, a light guide plate, or the like, and thus the user is allowed to recognize a virtual image.
PTL 1 discloses a system in which the head mounted display apparatus is used, which improves display of information in a medical environment. In the technology disclosed in PTL 1, information is acquired from a plurality of information sources based on a query. The acquired information undergoes a filtering process based on rules and is projected on eyepieces of a headset-type eyeglass viewer. In the technology disclosed in PTL 1, a control right and a priority right for display of the information on a fixed large display are determined based on a visual line of a person that wears the head mounted display apparatus. PTL 2 discloses a face mounted video display apparatus for medical use (a head mounted display apparatus). In the technology disclosed in PTL 2, operation state information of peripheral devices of an endoscope, which are used with the endoscope for an endoscopic examination or an endoscopic surgery, is displayed on the head mounted display apparatus. PTL 3 and PTL 4 disclose a method in which an augmented reality technology is applied to display information of a dental surgery in the head mounted display apparatus. In the technology disclosed in PTL 3 and PTL 4, display of a preoperative image, a simulated image, or the like for an operated part is superimposed on an actual image of an operated part.